Because of the recent demand for computerized data processing, larger capacities are demanded for media storage devices for magnetic disk devices and optical disk devices for storing data. For this, the track density and recording density of disk media are constantly increasing.
In such a data storage device, a write error may occur when writing data to a disk because of an off track of the head. In other words, when data is written to a recording medium, a shift in the position of the write head from the center of the target track is detected, and when this shift amount exceeds a predetermined threshold, this writing is determined as an off track error, and write retry is executed.
If the shift amount of the head position is too large, it is possible that the write data was written in an adjacent track. Therefore in addition to the decision standard of an off track error, a decision standard on whether data may have been written on an adjacent track is set, so that the read and rewrite of the adjacent track are executed at the same time with the retry of this write command (data write on the track of the write command) (U.S. Pat. No. 3,942,483, U.S. Pat. No. 3,037,250 and Japanese Patent Application Laid-Open No. 2001-014606). In other words, in prior art, rewrite on the adjacent track is executed continuously after a retry of the write command.
Along with the recent improvement of recording densities of disk storage devices, track pitch is decreasing. This results in the off track of a head increasing. In particular, according to decrease of the track pitch decreases, the probability of off track caused by vibration increases.
When rewrite on an adjacent track is continuously executed after a retry of the write command as in the case of a prior art, the rewrite may be subject to vibration, which caused an off track error to this write command. In other words, elements which cause an off track error still exist during execution of the rewrite processing, and a worse case scenario is that more off track writing may occur.
Immediately executing rewrite processing also leads to an increase in the execution of the write command, and causes a drop in performance of the drive.